The present invention relates to the transfer of articles, such as semiconductor wafers, and more particularly to a dual-blade robot for effecting independent linear transfer of two or more semiconductor wafers.
The use of robot arms is a well established manufacturing expedient in applications where human handling of the wafers is inefficient and/or undesired. For example, in the semiconductor arts robot arms are used to handle wafers during various process steps. Such process steps include those which occur in a process chamber, e.g. etching, deposition, passivation, etc., where a sealed environment must be maintained to limit the likelihood of contamination and to ensure that various specific processing conditions are provided.
Current practice includes the use of one or more robot arms to load semiconductor wafers from a wafer cassette into various processing ports within a multiple process chamber system. Such systems typically include a central chamber, to which the wafer cassette and process chambers are linked. The robot arm is then employed to retrieve the wafer from a particular port after processing within an associated process chamber. The wafer is then shuttled by the robot arm to a next port for additional processing. When all processing within the reaction system is complete, the robot arm returns the semiconductor wafer to the loading port. Typically, a stack of several semiconductor wafers is handled in this manner during each process run, and several wafers may be in process at any point in time.
In multiple process chamber systems, it is desirable to have more than one semiconductor wafer in process at a time. In this way, the process system is used to obtain maximum throughput. In the art, where a single robot arm is used in a process system to shuttle wafers between wafer cassettes and process chambers, the robot may require complex movement to simply switch two wafers in two single wafer process chambers.
One way to increase the efficiency of the robot is to provide a robot arm having the ability to handle two wafers at the same time. Thus, some equipment manufacturers have provided a robot arm in which the two robot blades are rotated about a pivot by a motor with a belt drive at the end of the arm. In this way, one wafer may be stored on one carrier while the other carrier is used to retrieve and place a second wafer. The carriers are then rotated and the stored wafer may be placed as desired. Such mechanism is rather complex and requires a massive arm assembly to support the weight of a carrier drive located at the end of an extendible robot arm. Furthermore, such a mechanism does not allow independent operation of the two carriers.